Gran Paradiso Alpha 2 is an early developer milestone for the next major version of Firefox that is being built on top of the next generation of Mozilla's layout engine, Gecko 1.9. Gran Paradiso Alpha 2 is being made available for testing purposes only, and is intended for web application developers and our testing community. Current users of Mozilla Firefox should not use Gran Paradiso Alpha 2.

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Maybe it's wise to stay clear of it for the time being, if you're not a tester/developer.
It's not for every day use it's an alpha.

I've checked out the Alpha 2 of Gran Paradiso when it was first released, cosmetically there's nothing new - the only change is the newer gecko engine AFAIK. I didn't really notice any quicker rendering, it's stable on this system.